Burn (Ex)

A magma elemental’s burn DC includes a –2 racial penalty, as their fires don’t burn quite as hot as true elemental flames.

Earth Glide (Ex)

A burrowing magma elemental can pass through stone, dirt, lava, or almost any other sort
of earth except metal as easily as a fish swims through water. Its
burrowing leaves behind no tunnel or hole, nor does it create any
ripple, though the area it passes through feels warm for 1 round
afterward and often retains a strangely smooth texture, as if the stone
had been polished. A move earth
spell cast on an area containing a burrowing magma elemental flings the
elemental back 30 feet, stunning the creature for 1 round unless it
succeeds on a DC 15 Fortitude save.

Lava Puddle (Su)

Once per day as a full-round action, a magma elemental can vomit forth a puddle of lava that fills its space to a depth of
2–3 inches and counts as difficult terrain. Any creature that moves
through this puddle of lava takes 2d6 points of fire damage. This damage
continues for 1d3 rounds after the creature leaves the lava pool,
although then it only inflicts 1d6 points of fire damage per round. The
lava puddle solidifies and is safe to touch after a number of rounds equal to the elemental’s Hit Dice. At the GM’s discretion, this puddle of lava could start secondary fires.

Paizo Core

In the border areas between the Plane of Earth and Plane of Fire,
volcanoes and continent-sized lava flows are commonplace. Elementals in
this area tend to have aspects of both planes, and the typical sort is
the magma elemental, an earth elemental with a core of liquid fire.
Magma elementals generally have a somewhat feral or bestial appearance.